Case study of stratospheric gravity waves of convective origin over Arctic Scandinavia – VHF radar observations and numerical modelling

摘要

Orography is a well-known source of gravity and inertia-gravity waves in theatmosphere. Other sources, such as convection, are also known to bepotentially important but the large amplitude of orographic waves overScandinavia has generally precluded the possibility to study such othersources experimentally in this region. In order to better understand theorigin of stratospheric gravity waves observed by the VHF radar ESRAD (Esrange MST radar) overKiruna, in Arctic Sweden (67.88° N, 21.10° E),observations have been compared to simulations made using the WeatherResearch and Forecasting model (WRF) with and without the effects oforography and clouds. This case study concerns gravity waves observed from00:00 UTC on 18 February to 12:00 UTC on 20 February 2007. We focus on thewave signatures in the static stability field and vertical wind deduced fromthe simulations and from the observations as these are the parameters whichare provided by the observations with the best height coverage. As is commonat this site, orographic gravity waves were produced over the Scandinavianmountains and observed by the radar. However, at the same time, southwardpropagation of fronts in the Barents Sea created short-period waves whichpropagated into the stratosphere and were transported, embedded in thecyclonic winds, over the radar site.